Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07D—HETEROCYCLIC COMPOUNDS
  • C07D249/00—Heterocyclic compounds containing five-membered rings having three nitrogen atoms as the only ring hetero atoms
  • C07D249/02—Heterocyclic compounds containing five-membered rings having three nitrogen atoms as the only ring hetero atoms not condensed with other rings
  • C07D249/08—1,2,4-Triazoles; Hydrogenated 1,2,4-triazoles
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07D—HETEROCYCLIC COMPOUNDS
  • C07D231/00—Heterocyclic compounds containing 1,2-diazole or hydrogenated 1,2-diazole rings
  • C07D231/02—Heterocyclic compounds containing 1,2-diazole or hydrogenated 1,2-diazole rings not condensed with other rings
  • C07D231/10—Heterocyclic compounds containing 1,2-diazole or hydrogenated 1,2-diazole rings not condensed with other rings having two or three double bonds between ring members or between ring members and non-ring members
  • C07D231/12—Heterocyclic compounds containing 1,2-diazole or hydrogenated 1,2-diazole rings not condensed with other rings having two or three double bonds between ring members or between ring members and non-ring members with only hydrogen atoms, hydrocarbon or substituted hydrocarbon radicals, directly attached to ring carbon atoms
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07D—HETEROCYCLIC COMPOUNDS
  • C07D233/00—Heterocyclic compounds containing 1,3-diazole or hydrogenated 1,3-diazole rings, not condensed with other rings
  • C07D233/54—Heterocyclic compounds containing 1,3-diazole or hydrogenated 1,3-diazole rings, not condensed with other rings having two double bonds between ring members or between ring members and non-ring members
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07D—HETEROCYCLIC COMPOUNDS
  • C07D233/00—Heterocyclic compounds containing 1,3-diazole or hydrogenated 1,3-diazole rings, not condensed with other rings
  • C07D233/54—Heterocyclic compounds containing 1,3-diazole or hydrogenated 1,3-diazole rings, not condensed with other rings having two double bonds between ring members or between ring members and non-ring members
  • C07D233/56—Heterocyclic compounds containing 1,3-diazole or hydrogenated 1,3-diazole rings, not condensed with other rings having two double bonds between ring members or between ring members and non-ring members with only hydrogen atoms or radicals containing only hydrogen and carbon atoms, attached to ring carbon atoms

Definitions

• the present invention relates to a process for preparing purified 1,3-substituted imidazolium salts of the formula (I)
• the radicals R 1 , R 2 , R 3 and R 4 are as defined above and the anion Y y ⁇ is the partly or fully deprotonated anion of an inorganic or organic protic acid H y Y (IV), where y is a positive integer and indicates the charge on the anion, with a strong base at from 20 to 250° C. while distilling off the 1,3-substituted imidazol-2-ylidene formed.
• 1,3-Substituted imidazolium salts belong to the group of ionic liquids and are becoming increasingly important. They represent, for example, good solvents for organic and inorganic compounds in a variety of applications.
• Ionic liquids are becoming increasingly important as solvents, for example for carrying out chemical reactions.
• P. Wasserscheid et al., Angew. Chem. 112 (2000), pages 3926 to 3945 give an overview of the use of these liquids in homogeneous transition metal catalysis.
• the purity of the ionic liquid used is of great importance here, since impurities generally have an adverse effect on the course of the chemical reactions.
• P. Dyson et al. in Electrochemical Society Proceedings, Volume 99-41, pages 161 to 168 refer to problems when using chloride-containing ionic liquids in liquid-phase hydrogenation and in the Suzuki reaction. For this reason, the purity of the desired product has to meet demanding requirements in the preparation of ionic liquids.
• ionic liquids comprises substituted imidazolium salts. In general, these are obtained from the corresponding N-substituted imidazole by alkylation of the second nitrogen.
• WO 02/34722 describes two different routes for preparing 1,2,3-substituted, 1,2,3,4-substituted and 1,2,3,4,5-substituted imidazolium salts: (1) In the indirect route, the appropriate substituted imidazole is reacted with an organic halide and the halide ion of the substituted imidazolium halide is replaced by the desired anion by means of ion exchange. (2) In the direct route, the appropriate substituted imidazole is reacted with an alkyl triflate or a trialkyloxonium salt of the desired anion (e.g. triethyloxonium tetrafluoroborate).
• an alkyl triflate or a trialkyloxonium salt of the desired anion e.g. triethyloxonium tetrafluoroborate.
• Disadvantages of the preparation via the indirect route (1) are the high cost of the ion exchange which is subsequently required and the extraction of the product with an organic solvent which may be associated therewith and also the residual content of halide ions which, for example, can have an adverse effect on the reactions catalyzed by transition metals.
• a disadvantage of the preparation via the direct route (2) is that the alkylating reagent determines both the substituent and the anion and the variation range and flexibility in respect of the anion is thus restricted.
• EP-A 1 182 196 teaches the halide-free preparation of 1,3-substituted imidazolium salts by reaction of the parent 1-substituted imidazole with the appropriate organic disulfate as alkylating agent and subsequent ion exchange with a metal salt comprising the desired anion.
• 1-butyl-3-methylimidazolium tetrafluoroborate is prepared by reacting 1-butylimidazole with dimethyl sulfate, subsequently treating the intermediate with sodium tetrafluoroborate and extracting the product a number of times with methylene chloride.
• WO 01/40146 describes the preparation of 1,3-substituted imidazolium salts by reaction of the parent 1-substituted imidazole with a fluorinated ester, for example a trifluoroacetic ester, or an alkyl sulfonate as alkylating agent in the presence of a solvent.
• a fluorinated ester for example a trifluoroacetic ester
• an alkyl sulfonate as alkylating agent
• a subsequent reaction of the product obtained with the acid of the desired anion for example tetrafluoroboric acid or hexafluorophosphoric acid, gives the desired 1,3-substituted imidazolium salt in virtually halide-free and metal-free form.
• a disadvantage of this process is the contamination of the desired 1,3-substituted imidazolium salt with traces of the compounds used in the synthesis or their reaction products, for example excess alkylating agent, salts of the 1-substituted imidazole used, the solvent used or the 1,3-substituted imidazolium salt of the fluorinated acid anion or the sulfonate.
• WO 96/18459 discloses the preparation of halide-free ionic liquids by reaction of a halide of the desired imidazolium, pyridinium or phosphonium cation with a lead salt whose anion represents the desired anion for the ionic liquid and removal of the precipitated lead halide.
• Disadvantages of the process described are the use of stoichiometric amounts of toxic lead salts and the associated formation of stoichiometric amounts of lead halides to be disposed of and also, in particular, the significant contamination of the product with these lead compounds, as indicated, in particular, by J. T. Hamill et al., Chem. Comm. 2000, pages 1929 to 1930.
• a disadvantage of the abovementioned processes for preparing substituted imidazolium salts is the formation of a product contaminated with by-products, which can lead to adverse effects in use of the substituted imidazolium salts.
• WO 01/77081 discloses a process in which purified 1,3-substituted imidazolium salts which are contaminated neither with halide ions nor with metal ions can be prepared.
• the starting material is a 1,3-substituted imidazolium salt which has been prepared, for example, by a conventional route, with the anion being able to be different from the anion desired later.
• the 1,3-substituted imidazolium salt is heated in the presence of a strong base, for example an alkoxide, under reduced pressure, with the corresponding 1,3-substituted imidazolium-carbene being formed and distilled off. This is condensed as a pure material in a receiver.
• the condensed carbene is subsequently reacted with the acid of the desired anion or an alcohol to form the purified 1,3-substituted imidazolium salt.
• a disadvantage of this process is the fact that, as described in A. J. Arduengo et al., J. Am. Chem. Soc. 114, 1992, pages 5530 to 5534, although carbenes which are not strongly sterically hindered are stable for some days in solution, the pure substance is very unstable. Thus, for example, pure 1,3-dimethylimidazol-2-ylidene decomposes even at low temperatures so as to become brown and form a viscous product.
• the amount of the viscous by-products increases further as a result of the increased residence time as the size of the production batch increases, so that only a highly contaminated product can be obtained when the process is carried out on an industrial scale.
• Intensive cooling of the distillation receiver to below 0° C. is very costly and energy-consuming in industry.
• the radicals R 1 , R 2 , R 3 and R 4 are as defined above and the anion Y y ⁇ is the partly or fully deprotonated anion of an inorganic or organic protic acid H y Y (IV), where y is a positive integer and indicates the charge on the anion, with a strong base at from 20 to 250° C.
• the purified 1,3-substituted imidazolium salt (I) which can be prepared by the process of the present invention comprises the 1,3-substituted imidazolium cation of the formula (Ia)
• Possible heteroatoms are in principle all heteroatoms which are able to formally replace a —CH 2 —, a —CH ⁇ , a C ⁇ or a ⁇ C ⁇ group.
• the carbon-comprising radical comprises heteroatoms, preference is given to oxygen, nitrogen, sulfur, phosphorus and silicon.
• Preferred groups are, in particular, —O—, —S—, —SO—, —SO 2 —, —NR—, —N ⁇ , —PR—, —PR 2 and —SiR 2 —, where the radical R is the remaining part of the carbon-comprising radical.
• R 2 and R 3 the carbon-comprising radical can also be bound directly via the heteroatom to the imidazolium ring.
• Possible functional groups are in principle all functional groups which can be bound to a carbon atom or a heteroatom.
• suitable groups are —OH (hydroxy), ⁇ O (in particular as a carbonyl group), —NH 2 (amino), ⁇ NH (imino), —COOH (carboxyl), —CONH 2 (carboxamide) and —CN (cyano).
• Functional groups and heteroatoms can also be directly adjacent, so that combinations of a plurality of adjacent atoms such as —O— (ether), —S— (thioether), —COO— (ester), —CONH— (secondary amide) or —CONR— (tertiary amide) are also encompassed, for example di(C 1 -C 4 -alkyl)amino, C 1 -C 4 -alkyloxy-carbonyl or C 1 -C 4 -alkyloxy.
• Halogens which may be mentioned are fluorine, chlorine, bromine and iodine.
• the process of the present invention is preferably used to prepare purified 1,3-substituted imidazolium salts (I) in which the radicals R 2 and R 3 are each, independently of one another,
• C 1 -C 18 -Alkyl which may be substituted by functional groups, aryl, alkyl, aryloxy, alkyloxy, halogen, heteroatoms and/or heterocycles is preferably methyl, ethyl, 1-propyl, 2-propyl, 1-butyl, 2-butyl, 2-methyl-1-propyl(isobutyl), 2-methyl-2-propyl(tert-butyl), 1-pentyl, 2-pentyl, 3-pentyl, 2-methyl-1-butyl, 3-methyl-1-butyl, 2-methyl-2-butyl, 3-methyl-2-butyl, 2,2-dimethyl-1-propyl, 1-hexyl, 2-hexyl, 3-hexyl, 2-methyl-1-pentyl, 3-methyl-1-pentyl, 4-methyl-1-pentyl, 2-methyl-2-pentyl, 3-methyl-2-pentyl, 4-methyl-2-pentyl, 2-methyl-3-pentyl
• C 6 -C 12 -Aryl which may be substituted by functional groups, aryl, alkyl, aryloxy, alkyloxy, halogen, heteroatoms and/or heterocycles is preferably phenyl, tolyl, xylyl, ⁇ -naphthyl, ⁇ -naphthyl, 4-diphenylyl, chlorophenyl, dichlorophenyl, trichlorophenyl, difluorophenyl, methylphenyl, dimethylphenyl, trimethylphenyl, ethylphenyl, diethylphenyl, isopropylphenyl, tert-butylphenyl, dodecylphenyl, methoxyphenyl, dimethoxyphenyl, ethoxyphenyl, hexyloxyphenyl, methylnaphthyl, isopropylnaphthyl, chloronaphthy
• a five- to six-membered oxygen-, nitrogen- and/or sulfur-containing heterocycle which may be substituted by functional groups, aryl, alkyl, aryloxy, alkyloxy, halogen, heteroatoms and/or heterocycles is preferably furyl, thienyl, pyrryl, pyridyl, indolyl, benzoxazolyl, dioxolyl, dioxyl, benzimidazolyl, benzothiazolyl, dimethylpyridyl, methylquinolyl, dimethylpyrryl, methoxyfuryl, dimethoxypyridyl or difluoropyridyl.
• the adjacent radicals R 1 and R 2 , R 2 and R 3 or R 3 and R 4 together form an unsaturated, saturated or aromatic ring which may be substituted by functional groups, aryl, alkyl, aryloxy, alkyloxy, halogen, heteroatoms and/or heterocycles and may be interrupted by one or more oxygen and/or sulfur atoms and/or one or more substituted or unsubstituted imino groups
• the two adjacent radicals preferably form a 1,3-propylene, 1,4-butylene, 2-oxa-1,3-propylene, 1-oxa-1,3-propylene, 2-oxa-1,3-propylene, 1-oxa-1,3-propenylene, 1-aza-1,3-propenylene, 1-C 1 -C 4 -alkyl-1-aza-1,3-propenylene, 1,4-buta-1,3-dienylene, 1-aza-1,4-buta-1,3-dienylene or 2-aza-1,
• radicals comprise oxygen and/or sulfur atoms and/or substituted or unsubstituted imino groups
• the number of oxygen and/or sulfur atoms and/or imino groups is not subject to any restrictions. There are generally no more than 5 of them present in the radical, preferably not more than 4 and very particularly preferably not more than 3.
• radicals comprise heteroatoms
• the radicals R 1 and R 4 are particularly preferably each, independently of one another, unbranched or branched C 1 -C 12 -alkyl such as methyl, ethyl, 1-propyl, 2-propyl, 1-butyl, 2-butyl, 2-methyl-1-propyl(isobutyl), 2-methyl-2-propyl (tert-butyl), 1-pentyl, 2-pentyl, 3-pentyl, 2-methyl-1-butyl, 3-methyl-1-butyl, 2-methyl-2-butyl, 3-methyl-2-butyl, 2,2-dimethyl-1-propyl, 1-hexyl, 2-hexyl, 3-hexyl, 2-methyl-1-pentyl, 3-methyl-1-pentyl, 4-methyl-1-pentyl, 2-methyl-2-pentyl, 3-methyl-2-pentyl, 4-methyl-2-pentyl, 2-methyl-3-pentyl, 3-methyl-3-pentyl, 2,2-dimethyl-1
• the radicals R 2 and R 3 are particularly preferably each, independently of one another, hydrogen or unbranched or branched C 1 -C 12 -alkyl such as methyl, ethyl, 1-propyl, 2-propyl, 1-butyl, 2-butyl, 2-methyl-1-propyl(isobutyl), 2-methyl-2-propyl(tert-butyl), 1-pentyl, 2-pentyl, 3-pentyl, 2-methyl-1-butyl, 3-methyl-1-butyl, 2-methyl-2-butyl, 3-methyl-2-butyl, 2,2-dimethyl-1-propyl, 1-hexyl, 2-hexyl, 3-hexyl, 2-methyl-1-pentyl, 3-methyl-1-pentyl, 4-methyl-1-pentyl, 2-methyl-2-pentyl, 3-methyl-2-pentyl, 4-methyl-2-pentyl, 2-methyl-3-pentyl, 3-methyl-3-pentyl, 2,2-di
• the process of the present invention is very particularly preferably used to prepare a purified 1,3-substituted imidazolium salt (I) in which the radicals R 1 and R 4 are each, independently of one another, methyl, ethyl, 1-propyl, 2-propyl, 1-butyl, 1-pentyl, 1-hexyl, 1-heptyl, 1-octyl, 1-nonyl, 1-decyl, 1-dodecyl, 1-tetradecyl, 1-hexadecyl, 1-octadecyl, 1-(2-ethyl)hexyl, benzyl, 3-phenylpropyl, 6-hydroxyhexyl or phenyl and the radicals R 2 and R 3 are each, independently of one another, hydrogen, methyl, ethyl, n-propyl, 2-propyl, 1-butyl, 1-hexyl, 6-hydroxyhexyl, phenyl or chlorine.
• the process of the present invention is very particularly preferably used for preparing a purified 1,3-substituted imidazolium salt (I) whose 1,3-substituted imidazolium cation is 1,3-dimethylimidazolium, 1-ethyl-3-methylimidazolium, 1-methyl-3-propylimidazolium, 1-isopropyl-3-methylimidazolium, 1-butyl-3-methylimidazolium, 1-methyl-3-pentylimidazolium, 1-hexyl-3-methylimidazolium, 1-heptyl-3-methylimidazolium, 1-methyl-3-octylimidazolium, 1-decyl-3-methylimidazolium, 1-methyl-3-benzyl-imidazolium, 1-methyl-3-(3-phenylpropyl)imidazolium, 1-(2-ethyl)hexyl-3-methyl-imidazolium, 1-methyl-3-n
• the purified 1,3-substituted imidazolium salt (I) which can be prepared by the process of the present invention comprises the anion A a ⁇ which is the partly or fully deprotonated anion of an inorganic or organic protic acid H a A (III), where a is a positive integer and indicates the charge on the anion.
• a partly deprotonated anion is an anion of a polybasic acid which still comprises one or more deprotonatable hydrogen atoms.
• a fully deprotonated anion is an anion which comprises no further deprotonatable hydrogen atoms.
• the process of the present invention is preferably used for preparing purified 1,3-substituted imidazolium salts (I) in which the anion A a ⁇ is
• R m to R o are each, independently of one another, hydrogen or a carbon-comprising organic, saturated or unsaturated, acyclic or cyclic, aliphatic, aromatic or araliphatic radical which has from 1 to 30 carbon atoms and may comprise one or more heteroatoms and/or be substituted by one or more functional groups or halogens; organic sulfate of the formula (Vi) [R p O—SO 3 ] ⁇ , where R p is a carbon-comprising organic, saturated or unsaturated, acyclic or cyclic, aliphatic, aromatic or araliphatic radical which has from 1 to 30 carbon atoms and may comprise one or more heteroatoms and/or be substituted by one or more functional groups or halogens; or halometalate of the formula (Vj) [M q Hal r ] s ⁇ , where M is a metal and Hal is fluorine, chlorine, bromine or iodine, q and
• the charge “a ⁇ ” on the anion A a ⁇ is “1 ⁇ ”, “2 ⁇ ” or “3 ⁇ ”.
• Examples of doubly negatively charged anions are sulfate, hydrogenphosphate and carbonate.
• An example of a triply negatively charged anion is phosphate.
• heteroatoms are in principle all heteroatoms which are able formally to replace a —CH 2 —, a —CH ⁇ , a C ⁇ , or a ⁇ C ⁇ group.
• the carbon-comprising radical comprises heteroatoms, preference is given to oxygen, nitrogen, sulfur, phosphorus and silicon.
• Particularly preferred groups are —O—, —S—, —SO—, —SO 2 —, —NR—, —N ⁇ , —PR—, —PR 2 and —SiR 2 —, where the radicals R are in each case the remaining part of the carbon-comprising radical.
• Possible functional groups are in principle all functional groups which can be bound to a carbon atom or a heteroatom.
• suitable groups are —OH (hydroxyl), ⁇ O (especially as a carbonyl group), —NH 2 (amino), ⁇ NH (imino), —COOH (carboxyl), —CONH 2 (carboxamide) and —CN (cyano).
• Functional groups and heteroatoms can also be directly adjacent, so that combinations of a plurality of adjacent atoms such as —O— (ether), —S— (thioether), —COO— (ester), —CONH— (secondary amide) or —CONR— (tertiary amide) are also included.
• Halogens which may be mentioned are fluorine, chlorine, bromine and iodine.
• anion A a ⁇ is a tetrasubstituted borate (Va) [BR a R b R c R d ] ⁇
• Particularly preferred tetrasubstituted borates (Va) are tetrafluoroborate, tetraphenylborate and tetra[3,5-bis(trifluoromethyl)phenyl]borate.
• the anion A a ⁇ is an organic sulfonate (Vb) [R e —SO 3 ] ⁇
• the radical R e is preferably methyl, trifluoromethyl, pentafluoroethyl, p-tolyl or C 9 F 19 .
• Particularly preferred organic sulfonates (Vb) are trifluoromethanesulfonate (triflate), methanesulfonate, p-toluenesulfonate, nonadecafluorononanesulfonate (nonaflate), dimethylene glycol monomethyl ether sulfate and octylsulfate.
• the radical R f is preferably hydrogen, trifluoromethyl, pentafluoroethyl, phenyl, hydroxyphenylmethyl, trichloromethyl, dichloromethyl, chloromethyl, trifluoromethyl, difluoromethyl, fluoromethyl, ethenyl(vinyl), 2-propenyl, —CH ⁇ CH—COO ⁇ , cis-8-heptadecenyl, —CH 2 —C(OH)(COOH)—CH 2 —COO ⁇ or unbranched or branched C 1 -C 18 -alkyl such as methyl, ethyl, 1-propyl, 2-propyl, 1-butyl, 2-butyl, 2-methyl-1-propyl(isobutyl), 2-methyl-2-propyl(tert-butyl), 1-pentyl, 2-
• Particularly preferred carboxylates (Vc) are formate, acetate, propionate, butyrate, valerate, benzoate, mandelate, trichloroacetate, dichloroacetate, chloroacetate, trifluoroacetate, difluoroacetate, fluoroacetate.
• anion A a ⁇ is a (fluoroalkyl)fluorophosphate (Vd) [PF x (C y F 2y+1 ⁇ z H z ) 6 ⁇ x ] ⁇
• z is preferably 0.
• the radicals R g to R l are preferably each, independently of one another, trifluoromethyl, pentafluoroethyl, phenyl, trichloromethyl, dichloromethyl, chloromethyl, trifluoromethyl, difluoromethyl, fluoromethyl or unbranched or branched C 1 -C 12 -alkyl such as methyl, ethyl, 1-propyl, 2-propyl, 1-butyl, 2-butyl, 2-methyl-1-propyl(isobutyl), 2-methyl-2-propyl(tert-butyl), 1-pentyl, 2-pentyl,
• Particularly preferred imides (Ve), (Vf) and (Vg) are [F 3 C—SO 2 —N—SO 2 —CF 3 ] ⁇ (bis(trifluoromethylsulfonyl)imide), [F 5 C 2 —SO 2 —N—SO 2 —C 2 F 5 ] ⁇ (bis(pentafluoroethylsulfonyl)imide), [F 3 C—SO 2 —N—CO—CF 3 ] ⁇ , [F 3 C—CO—N—CO—CF 3 ] ⁇ and those in which the radicals R g to R l are each, independently of one another, methyl, ethyl, propyl, butyl, phenyl, trichloromethyl, dichloromethyl, chloromethyl, trifluoromethyl, difluoromethyl or fluoromethyl.
• the radicals R m to R o are preferably each, independently of one another, trifluoromethyl, pentafluoroethyl, phenyl, trichloromethyl, dichloromethyl, chloromethyl, trifluoromethyl, difluoromethyl, fluoromethyl or unbranched or branched C 1 -C 12 -alkyl such as methyl, ethyl, 1-propyl, 2-propyl, 1-butyl, 2-butyl, 2-methyl-1-propyl(isobutyl), 2-methyl-2-propyl(tert-butyl), 1-pentyl, 2-pentyl, 3-pentyl, 2-methyl-1-butyl, 3-methyl-1-butyl, 2-methyl-2-butyl, 3-methyl-2-butyl, 2,2-dimethyl-1-propyl, 1-hexyl, 2-hexyl, 3-hexyl, 2-methyl-1-pentyl, 3-methyl-1-pentyl, 4-methyl-1-
• Particularly preferred methides (Vh) are [(F 3 C—SO 2 ) 3 C] ⁇ (tris(trifluoromethylsulfonyl)methide), [(F 5 C 2 —SO 2 ) 3 C] ⁇ (bis(pentafluoroethylsulfonyl)methide) and those in which the radicals R m to R o are each, independently of one another, methyl, ethyl, propyl, butyl, phenyl, trichloromethyl, dichloromethyl, chloromethyl, trifluoromethyl, difluoromethyl or fluoromethyl.
• the radical R p is preferably a branched or unbranched C 1 -C 30 -alkyl radical and particularly preferably methylsulfate, ethylsulfate, propylsulfate, butylsulfate, pentylsulfate, hexylsulfate, heptylsulfate or octylsulfate.
• anion A a ⁇ is a halometalate (Vj) [M q Hal r ] s ⁇
• M is preferably aluminum, zinc, iron, cobalt, antimony or tin.
• Hal is preferably chlorine or bromine, very particularly preferably chlorine.
• q is preferably 1, 2 or 3 and r and s are determined by the stoichiometry and charge on the metal ion.
• the process of the present invention is very particularly preferably used to prepare a purified 1,3-substituted imidazolium salt (I) whose anion A a ⁇ is tetrafluoroborate, hexafluorophosphate, trifluoromethanesulfonate, methanesulfonate, formate, acetate, mandelate, nitrate, nitrite, trifluoroacetate, sulfate, hydrogensulfate, methylsulfate, ethylsulfate, propylsulfate, butylsulfate, pentylsulfate, hexylsulfate, heptylsulfate, octylsulfate, phosphate, dihydrogenphosphate, hydrogenphosphate, propionate, tetrachlorooaluminate, Al 2 Cl 7 ⁇ , chlorozincate, chloroferrate, bis(trifluoromethyls
• the purified 1,3-substituted imidazolium salt (I) prepared in the process of the present invention is very particularly preferably the tetrafluoroborate, hexafluorophosphate, trifluoromethanesulfonate, methanesulfonate, formate, acetate, trifluoroacetate, sulfate, hydrogensulfate, methylsulfate, ethylsulfate, propylsulfate, butylsulfate, pentylsulfate, hexylsulfate, heptylsulfate, octylsulfate, phosphate, dihydrogenphosphate, hydrogenphosphate, propionate, tetrachlorooaluminate, Al 2 Cl 7 ⁇ , chlorozincate, chloroferrate, bis(trifluoromethylsulfonyl)imide, bis(pentafluoroethylsulf
• the 1,3-substituted imidazolium salt (II) to be used in the process of the present invention comprises the 1,3-substituted imidazolium cation (Ia) as defined above which is identical to the 1,3-substituted imidazolium cation (Ia) of the purified 1,3-substituted imidazolium salt (I) to be prepared and the anion Y y ⁇ which is a partly or fully deprotonated anion of an inorganic or organic protic acid H y Y (IV), where y is a positive integer and indicates the charge on the anion.
• Y y ⁇ are in principle all partly or fully deprotonated anions of inorganic or organic protic acids which form salts with the 1,3-substituted imidazolium cation (Ia).
• Y y ⁇ is preferably a partly or fully deprotonated anion of an inorganic or organic protic acid as described in the definition of the anion A a ⁇ or chloride, bromide or iodide.
• a 1,3-substituted imidazolium salt (II) comprising chloride, bromide, methanesulfonate, hydrogencarbonate, carbonate, hydrogensulfate, diethylphosphate, tosylate or methylsulfate as anion Y y ⁇ in the process of the present invention.
• the 1,3-substituted imidazolium salt (II) to be used is obtainable, for example, by means of generally known syntheses, for instance by alkylation of the corresponding 1-substituted imidazole.
• strong bases it is in principle possible to use all bases which are able, under the given reaction conditions such as pressure and temperature, to convert the 1,3-substituted imidazolium salt (II) used into the corresponding 1,3-substituted imidazol-2-ylidene in the process of the present invention.
• suitable strong bases are alkoxides such as the alkali metal and alkaline earth metal salts of aliphatic alcohols, hydroxides such as the alkali metal and alkaline earth metal hydroxides (e.g.
• the 1,3-substituted imidazol-2-ylidene which has been distilled off and the protic acid H a A (III) are preferably brought into contact with one another in countercurrent, with the purified 1,3-substituted imidazolium salt (I) formed being condensed as a result of its high boiling point and conveyed downward, so that the purified 1,3-substituted imidazolium salt (I) can be obtained directly as desired end product.
• Reaction apparatuses suitable for this purpose are apparatuses in general in which two gas streams can be mixed or brought into contact, for example distillation columns or tube reactors.
• the 1,3-substituted imidazol-2-ylidene which has been distilled off is passed in the gaseous state into a receiver comprising the protic acid H a A (III) and the purified 1,3-substituted imidazolium salt (I) is isolated therefrom.
• suitable apparatuses are stirred vessels having a gas inlet device, stirred vessels provided with column, condenser and receiver. In general, it is advantageous to cool the receiver in order to counter vaporization of the protic acid (III) present in it.
• the gaseous 1,3-substituted imidazol-2-ylidene can be, for example, the gaseous overhead product from a distillation column or the gaseous stream directly from the apparatus in which the formation of the 1,3-substituted imidazol-2-ylidene occurs.
• the protic acid (III) is used in a stoichiometric or superstoichiometric amount based on the 1,3-substituted imidazol-2-ylidene. Excess protic acid (III) is then removed in a simple manner by distillation or liquid/liquid extraction after the reaction, so that the purified 1,3-substituted imidazolium salt (I) can be obtained directly as desired end product.
• the 1,3-substituted imidazol-2-ylidene which has been distilled off is condensed in a condenser, the condensate is passed into a distillation receiver comprising the protic acid H a A (III) and the purified 1,3-substituted imidazolium salt (I) is isolated therefrom.
• suitable apparatuses are stirred vessels having a gas inlet device. In general, it is advantageous to cool the receiver in order to counter vaporization of the protic acid (III) present in it.
• the protic acid (III) is used in a stoichiometric or superstoichiometric amount based on the 1,3-substituted imidazol-2-ylidene. Excess protic acid (III) is then removed in a simple manner by distillation or liquid/liquid extraction after the reaction, so that the purified 1,3-substituted imidazolium salt (I) can be obtained directly as desired end product.
• the process of the present invention makes it possible to prepare the 1,3-substituted imidazolium salts (I) in particularly high purity. If the chloride, bromide or iodide salt is not wanted as purified 1,3-substituted imidazolium salt (I), the total concentration of chloride, bromide and iodide ions is preferably ⁇ 100 ppm by weight, particularly preferably ⁇ 50 ppm by weight, very particularly preferably ⁇ 10 ppm by weight and in particular ⁇ 5 ppm by weight.
• the total metal concentration is preferably ⁇ 100 ppm by weight, particularly preferably ⁇ 50 ppm by weight, very particularly preferably ⁇ 10 ppm by weight and in particular ⁇ 1 ppm by weight.
• the total metal concentration is the total concentration of metal which is present in bound or unbound, uncharged or ionic form in solution or suspension in the molten 1,3-substituted imidazolium salt (I).
• the present invention provides a process for preparing purified 1,3-substituted imidazolium salts which has wide variability and flexibility in terms of the choice of substituents of the imidazolium cation and the choice of anion and leads, in a technically simple way, to high yields of pure to highly pure 1,3-substituted imidazolium salts.
• the process of the present invention can be carried out using 1,3-substituted imidazolium salts which have been prepared in any desired way. They can also comprise various impurities. The process of the present invention thus imposes no significant demands on the quality of the 1,3-substituted imidazolium salt used.
• the direct reaction of the gaseous 1,3-substituted imidazol-2-ylidene with the desired protic acid or the introduction of the gaseous or condensed 1,3-substituted imidazol-2-ylidene into a receiver comprising the protic acid prevents or at least significantly reduces the formation of any by-products or decomposition products from the reactive 1,3-substituted imidazol-2-ylidene.

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• 2003
  • 2003-07-21 DE DE10333239A patent/DE10333239A1/de not_active Withdrawn
• 2004
  • 2004-06-30 CN CNB2004800209399A patent/CN100404515C/zh not_active Expired - Fee Related
  • 2004-06-30 WO PCT/EP2004/007076 patent/WO2005019183A1/de active IP Right Grant
  • 2004-06-30 US US10/564,871 patent/US7501522B2/en not_active Expired - Fee Related
  • 2004-06-30 EP EP04740458A patent/EP1651614B1/de not_active Revoked
  • 2004-06-30 ES ES04740458T patent/ES2287742T3/es active Active
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  • 2004-06-30 JP JP2006520704A patent/JP2006528139A/ja not_active Withdrawn
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